Pleiades 12V battery powered 12AU7 microphone pre preamplifier or DI with positive bias resistor from plate (anode) to grid to free electrons

This is a mod of a pre amplifier made in around 2000 using an ECC86 which did not work quite well. Many years later it was replaced with 12AU7 at 12V and then after some time  the other end of the 10Mohms grid resistor was connected to Anode where it started to sing.







 Inside view showing 10MOhms from plate to grid. ECC82; sounds great but EF183 is possibly more suitable for low voltage positive grid bias work.